One man's attempt at opting out of the total car culture by walking, busing, and cycling in Omaha, Nebraska.

Monday, October 4, 2010

Skinny Rims, Fat Tires

If Fat Tire is a beer, then perhaps Skinny Rim could be an energy drink.

Actually, this post is about trying to winterize my new Trek Earl. My plan is to put Nokian Hakkapeliitta 700c x 35mm studded tires underneath full fenders and a low gearing ratio on its single speed drivetrain so I can pedal out of snow drifts and slowly up steep hills.

When I bought the bike, the shop mechanic assured me that I could fit the 35mm tires on the rims that were sold with 28mm tires. Yesterday, I tried mounting the tire, just to see how it would fit.

The rims are stamped at 14mm. Upon researching tire fit online, I found (you guessed it) that Sheldon had a great chart that shows tire/rim compatibility. This chart delivered a bit of bad news, in that my 14mm rims are not depicted holding a tire much larger than 28mm; a difference of 7mm. However, there's a note that says the dimensions depicted may be conservative.

It took a bit of persuasion with a plastic tire lever to get the snow tire on my rim. As I tried to pump it up with air, I heard an odd creaky noise, followed by a loud pop as the tube herniated through an improperly set bead.

Hmm.

I searched my closet and found, thankfully, another tube with a Schrader valve. I made extra special sure that the bead was set as I remounted the tire, as well as spot checked it as I pumped. Finally I mounted the wheel back on the bike to check for clearance.

It looks good!

My question to any readers: do you have experience in mounting wide tires on narrow rims. Is the 35mm on a 14mm pushing it too far? I won't know how the bike feels until I can get the tires remounted and go for a test spin, though I'd feel silly riding a studded tire around in October while it's still 75 degrees outside.

I may consider a brake upgrade, as the check stock brake has no quick release to facilitate tire changes. I put Tektro brakes on my Schwinn Le Tour II, and I like them, so I may consider a similar brake for the Earl.

My next step is to put on a bigger freewheel. I've got a 22 tooth freewheel on the way.

I'm not in a hurry to see the snow, but I'll be eager to give the Earl a whirl.

14 comments:

Hmm. Next time you have the tire off the rim, you might want to measure that interior rim width. Cause 14mm seems awfully narrow. Mavic Open Pros are some of the skinniest rims around at 18 and change mms interior width. And on Open Pros, I've run Bonty 32C hardcase tires which really should be labeled 35C since they're HUGE.

A wider rim will help a wider tire sit more in the rim instead of on top of it, if that makes sense. This allows the tire to conform better to the road when you're cornering. How much this will help you when you've got a studded tire trudging through snow and ice, I'm unsure.

But yes, if the rim interior width really is 14mms, I'd be concerned with how well a 35C tire will stay put if the pressure runs low or you get a flat. But again, if your trudging through the snow, too low pressure or a flat is going to be a problem with any tire/rim setup.

I don't have any hard feelings, but I asked the shop guys about that, basically making them know that tire fit was the main reason I was buying the bike. I was assured that it would.

Since I did get the tires mounted, I think I can at least give it a shot.

I'll measure the rim's interior width and get back to you.

The question of what max size tire will fit on the stock Bontrager CR-65 was asked on the Earl page at the Trek site. The question was answered that they don't publish max tire widths, since it can vary greatly from among manufacturer's.

Would it make any difference to use a skinny or fat tube?

It looks like Nokian makes, or at least made, a 32mm version of their studded tire. I don't want to buy new tires, but that might be an option if I need a slightly skinnier snow tire.

Scott.. looking at the photo of the rim I'm thinking that the wheel size of 14mm is for the wheel rim depth. I think your width would actually be closer to 18-20. You can also see the rim looks like it's wider than it is deep. Grab your calipers and check. In any case, I think you would be just fine on your 35s. I run some 35s on my Velomax Circuits and also Rolfs (@18-19mm) without a problem. Only concern would be taking race course turns at high speed but that doesn't happen with these types of tires and I feel like I could even go a little wider without a problem.

Holy Moly Chris, you might have it! I didn't think a rim with a nearly 20mm outer width could only be 14 interior. But I guess if the hook for the beads is large or the rim is thicker material, then that would make sense.